Conventional magnetic disk drive designs comprise a commonly denominated contact start-stop (CSS) system commencing when the head begins to slide against the surface of the disk as the disk begins to rotate. Upon reaching a predetermined high rotational speed, the head floats in air at a predetermined distance above the surface of the disk due to dynamic pressure effects caused by air flow generated between the sliding surface of the head and the disk. During reading and recording operations, the transducer head is maintained at a controlled distance from the recording surface, supported on a bearing of air as the disk rotates, such that the head can be freely moved in both the circumferential and radial directions allowing data to be recorded on and retrieved from the surface of the disk at a desired position. Upon terminating operation of the disk drive, the rotational speed of the disk decreases and the head again begins to slide against the surface of the disk and eventually stops in contact with and pressing against the disk. Thus, the transducer head contacts the recording surface whenever the disk is stationary, accelerates from the stop and during deceleration just prior to completely stopping. Each time the head and disk assembly is driven, the sliding surface of the head repeats the cyclic operation consisting of stopping, sliding against the surface of the disk, floating in the air, sliding against the surface of the disk and stopping.
It is considered desirable during reading and recording operations to maintain each head as close to its associated recording surface as possible, i.e., to minimize the flying height of the head. Thus, a smooth recording surface is preferred, as well as a smooth opposing surface of the associated head, thereby permitting the head and the disk to be positioned in close proximity with an attendant increase in predictability and consistent behavior of the air bearing supporting the head. However, if the head surface and the recording surface are too flat, the precision match of these surfaces gives rise to excessive stiction. If limited torque provided by a drive's motor cannot overcome this stiction, the drive will fail to spin up. In addition, a flat-to-flat contact also gives rise to excessive friction during the start up and stopping phases, thereby causing wear to the head and recording surfaces eventually leading to what is referred to as a "head crash." Thus, there are competing goals of reduced head/disk stiction/ friction and minimum transducer flying height.
Conventional practices for addressing these apparent competing objectives involve providing a magnetic disk with a roughened recording surface to reduce the head/disk friction by techniques generally referred to as "texturing."Conventional texturing techniques involve polishing the surface of a disk substrate to provide a texture thereon prior to subsequent deposition of layers, such as an underlayer, a magnetic layer, a protective overcoat, and a lubricant topcoat, wherein the textured surface on the substrate is intended to be substantially replicated in the subsequently deposited layers.
A typical longitudinal recording medium is depicted in FIG. 1 and comprises a substrate 10, typically an aluminum (Al)-alloy, such as an aluminum-magnesium (Al--Mg)-alloy, plated with a layer of amorphous nickel-phosphorous (NiP). Alternative substrates include glass, ceramic, glass-ceramic materials and graphite. Substrate 10 typically contains sequentially deposited on each side thereof a chromium (Cr) or Cr-alloy underlayer 11, 11', a cobalt (Co)-base alloy magnetic layer 12, 12' a protective overcoat 13, 13', typically containing carbon, and a lubricant topcoat 14, 14'. Cr underlayer 11, 11' can be applied as a composite comprising a plurality of sub-underlayers 11A, 11A'. Cr underlayer 11, 11', Co-base alloy magnetic layer 12, 12' and protective carbon overcoat 13, 13' are usually deposited by sputtering techniques performed in an apparatus containing sequential deposition chambers. A conventional Al-alloy substrate is provided with a NiP plating, primarily to increase the hardness of the Al substrate, serving as a suitable surface for polishing to provide a texture which is substantially reproduced on the disk surface.
A conventional disk drive comprising a disk with a textured landing zone, such as that disclosed in Nguyen, U.S. Pat. No. 5,550,696, is schematically illustrated in FIG. 2. For illustrative convenience and ease of explanation, the disk drive depicted in FIG. 2 is shown with a single recording head and associated disk surface; however, conventional disk drives typically comprise multiple heads and multiple disks. The depicted disk drive comprises a base 20 to which are secured a disk drive motor with a rotatable spindle 21 and a head actuator 22. A magnetic recording medium (disk) 23 is connected to spindle 21 and rotated by the drive motor.
The disk 23 is typically a thin film disk, such as that illustrated in FIG. 1. A read/write head or transducer 24 is affixed under the trailing end of an air-bearing slider 25. Transducer 24 can be an inductive read/write transducer or an inductive write transducer with a magnetoresistive (MR) read transducer formed by conventional film deposition techniques. Slider 25 is connected to actuator 22 by rigid arm 26 and suspension 27 which provides a biasing force urging slider 25 onto the surface of recording disk 23. During operation of the disk drive, the drive motor rotates disk 23 at a constant speed, and actuator 22 pivots on shaft 28 to move the slider 25 generally radially across the surface of disk 23, so that the read/write transducer 25 can access different data tracts on disk 23. Actuator 22 is typically a rotary voice coil motor (VCM) having a coil 29 that moves through the fixed magnetic field of magnet assembly 200 when current is applied to the coil. The data detected from disk 23 by transducer 24 are processed into a data read back signal by signal amplification and processing circuitry in the integrated circuit chip 201 on arm 26. The signals from transducer 24 travel via flex cable 202 to chip 201 which outputs the signals via cable 203. A dedicated textured landing zone 204 is typically formed by laser texturing near the disk inside diameter away from the smooth disk data region 205. When the disk drive motor is stopped, slider 25 is in contact with the textured surface of landing zone 204.
A key performance requirement for a disk drive, particularly in mobile computing applications, is non-operational shock resistance. A sudden deceleration of a disk drive, which may occur when a computer is subjected to shock during an accident, can cause the read/write heads to separate from disks and subsequently impact on the disks, thereby damaging the disks. The severity of shock is typically proportional to the amount of deceleration a disk drive experiences.
Accordingly, a need exists for improved disk drives having non-operational shock resistance. A particular need exists for improved disk drives having non-operational shock resistance achieved by preventing the separation of the head from the disk.